Photomask and pattern forming method used in a thermal flow process and semiconductor integrated circuit fabricated using the thermal flow process

ABSTRACT

The invention relates to a photomask for use in a thermal flow process in which: a photomask is prepared in which a plurality of exposure openings are formed; a resist is applied to the surface of a layer of a semiconductor integrated circuit that is to undergo processing; this resist is patterned by an exposure process through the photomask to form a plurality of openings in the resist that correspond to each of the exposure openings; and the patterned resist is then heated to cause each of the openings to shrink; wherein at least a portion of exposure openings among the plurality of exposure openings are formed in shapes that compensate for anisotropic deformation that occurs in the openings when the patterned resist is heated to cause each of the openings to shrink. Since the openings that are formed in the resist are provided in advance with shapes that compensate for the deformation that occurs when the openings shrink, these openings attain the proper shape after undergoing shrinking and deformation.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a photomask used in a thermal flowprocess, a method of forming patterns used in a thermal flow process,and a semiconductor integrated circuit in which a portion having fineplanar shapes is treated by a prescribed process through openings in aresist.

2. Description of the Related Art

In recent years, fine-patterned semiconductor integrated circuitsconstructed by using thin-film techniques are being used for a varietyof purposes, and these constructions are increasing in fineness witheach year. As an example, photolithography is one technique forachieving fine patterning of the layers of a semiconductor integratedcircuit.

In a case of forming through-holes in the insulating film of asemiconductor integrated circuit, a resist is applied to the surface ofthe insulating film that is to undergo processing, and the resist isthen exposed using a photomask in which a plurality of exposure openingsare formed. The resist is then developed to form openings at the exposedportions, and this resist is used as a mask to etch the insulating filmthrough the openings.

This type of photolithography is used not only for the formation ofthrough-holes described above but for various other purposes such asintroducing impurities into a semiconductor substrate and patterningwiring lines. In this type of photolithography, a photomask is formed inwhich the pattern that is to be exposed is enlarged in all directions,following which the exposure process is carried out with this photomaskusing reducing optics to expose a pattern of the desired dimensions onthe resist.

In this technique, a pattern that is finer than a prescribed dimensioncannot be exposed due to the limits of optical resolution. However,there is now demand to reduce resist openings below the exposure limitdimensions, and the thermal flow process has been developed as a meansof realizing such a reduction.

Referring now to FIG. 1A-FIG. 2C, one example of the thermal flowprocess of the prior art is next described.

As shown in FIG. 1A, a DRAM (Dynamic Random Access Memory) that is inthe process of fabrication is first prepared as semiconductor integratedcircuit 100, which is the object of processing. In semiconductorintegrated circuit 100 that is here taken as an example, gate oxide film102 is formed on the surface of semiconductor substrate 101, and gateelectrodes 103 and 104 of the transistor elements that will serve asmemory cells are formed in a prescribed pattern on the surface of thisgate oxide film 102. Gate oxide film 102 is partitioned by elementisolation regions 105 according to the positions of memory cells, andthe space around gate electrodes 103 and 104 is filled with interlayerdielectric film 106, which is a prescribed layer.

In semiconductor integrated circuit 100 which is taken as an examplehere, contact hole 107 of a bit contact is formed from the surface ofinterlayer dielectric film 106 to the surface of gate oxide film 102 ata position between the pair of gate electrodes 103 and 104, as shown inFIG. 2C. Photomask 111, in which is formed exposure opening 110 thatcorresponds to this contact hole 107, is therefore prepared as shown inFIG. 1C.

The structure of this photomask 111 is such that shield film 113 isformed on the underside of transparent base member 112 and exposureopening 110 is formed by partially removing this shield film 113. Thisexposure opening 110 is formed at position that corresponds to contacthole 107, and its dimensions in all directions are greater than thedimensions of contact hole 107.

Resist 115 is then applied to the surface of interlayer dielectric film106, which is a prescribed layer of semiconductor integrated circuit100, to form a prescribed film thickness as shown in FIG. 1B, and theabove-described photomask 111 is arranged parallel to and confrontingthe surface of resist 115 at a prescribed distance from the surface ofresist 115.

In this configuration, resist 115 is exposed to light by exposure device(not shown in the figure) through exposure opening 110 of photomask 111,and as shown in FIG. 2A, this resist 115 is then developed to formopening 116 that corresponds to exposure opening 110. In thephotolithographic technique of the prior art, a contact hole is formedin interlayer dielectric film 106 of semiconductor integrated circuit100 through this opening 116 in resist 115.

However, since it is impossible to form contact hole 107 of a diameterthat is still smaller than the dimension limited by exposure resolution,resist 115 that has been patterned as described hereinabove is heatedand softened in a thermal flow process to shrink opening 116 as shown inFIG. 2B.

Since opening 116 of resist 115 thus attains a diameter that is smallerthan the exposure limit dimension, an extremely small diameter contacthole 107 can be formed from the surface of interlayer dielectric film106 to the surface of gate oxide film 102 by etching interlayerdielectric film 106 of semiconductor integrated circuit 100 throughopening 116 in resist 115.

Exposure opening 110 of photomask 111, which is used in the exposureprocess in the above-described thermal flow process, is therefore formedat dimensions that approach the limit dimensions of the exposure processand in a shape that is an enlargement in all directions of opening 116that has been shrunk by heating resist 115.

When the dimensions of exposure opening 110 approach the exposure limitdimensions, the shape of an exposure beam that passes through exposureopening 110 is deformed by such factors as diffraction. The shape of theexposure of opening 116 in resist 115 is therefore roughly oval in shapeeven though exposure opening 110 is square, and the shape of opening 116following the thermal flow process becomes approximately circular.

Since no problem is raised if the plan shape of contact hole 107 that isformed at the exposure limit dimensions as described above issubstantially circular, exposure opening 110 of photomask 111 istypically formed as a square in order to simplify design andfabrication. As a result, in a case in which the exposure dimension ofopening 116 in resist 115 is set to a circle of diameter “a”, exposureopening 110 of photomask 111 is formed as a square having sides oflength “a”.

In the interest of simplifying the explanation here, a case is describedin which the process of exposing resist 115 using photomask 111 iscarried out in equal proportions, but in a case in which the exposureprocess is performed in the above-described exposure limit dimensions,the pattern of openings of photomask 111 is typically exposed on resist115 in a form that is reduced by reduction optics.

After forming opening 116 in resist 115 by an exposure process usingphotomask 111 in the above-described thermal flow process, this resist115 is heated to shrink opening 116, whereby a process can be performedon interlayer dielectric film 106 at dimensions that are smaller thanthe exposure limit dimension.

Nevertheless, when resist 115 is heated and softened to shrink opening116 that was formed by the exposure process as described hereinabove,opening 116 deforms as it shrinks due to the surface tension of thisresist 115. It has been confirmed by the inventors of this inventionthat this deformation occurs in accordance with the positionalrelationships between the plurality of openings 116. Specifically, whenshrinking a plurality of openings 116 by heating resist 115, the degreeof shrinkage at each of openings 116 that are close to each other issmaller in the direction between openings 116 while the degree ofshrinking is greater in the direction orthogonal to this direction.

In some types of high-integration DRAM referred to as “¼ pitch DRAM,”for example, a plurality of contact holes 107 are arranged linearly in adirection that is inclined 45° from the directions of arrangement of thebit lines and word lines. Photomask 111 for forming such a plurality ofcontact holes 107 has a shape in which a plurality of square exposureopenings 110 are arranged in a line in a 45° direction, as shown in FIG.3A.

When resist 115 is exposed using this type of photomask 111, a pluralityof round openings 116 is thus arranged in a line in a 45° direction, asshown in FIG. 3B. When this resist 115 is heated and openings 116 arecaused to shrink, however, the degree of shrinkage in the direction ofarrangement is small, while the degree of shrinkage in the directionorthogonal to this direction is great, and, as shown in FIG. 3C, each ofopenings 116 therefore forms an oval that is elongated in the directionof arrangement of openings 116.

In a thermal flow process of the prior art, the formation of openings116 of a desired shape in desired positions is problematic due todeformation according to the positional relationship between theplurality of openings 116, as described in the foregoing explanation,and the proper realization of prescribed fine processing onsemiconductor integrated circuit 100 is therefore also problematic.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a photomask that canproperly realize prescribed fine processing on a semiconductorintegrated circuit in a thermal flow process; a pattern forming methodthat can properly realize prescribed fine processing on a semiconductorintegrated circuit in a thermal flow process; and a semiconductorintegrated circuit in which prescribed fine processing is properlyrealized.

According to one aspect of the present invention, a photomask is used ina thermal flow process in which: a photomask is prepared in which aplurality of exposure openings are formed; a resist is applied to thesurface of the layer of a semiconductor integrated circuit that is toundergo processing; the resist is patterned by an exposure processthrough the photomask to form a plurality of openings in the resist thatcorrespond to each of the exposure openings; and the resist in which thepatterning has been carried out is heated to cause each of the openingsto shrink; wherein at least a portion of the exposure openings among theplurality of exposure openings are formed in a shape that compensatesfor the anisotropic deformation that occurs in the openings when each ofthe openings is caused to shrink by heating the patterned resist. In thethermal flow process that uses the photomask of the present invention,when the resist that is applied to the surface of a layer of asemiconductor integrated circuit that is to undergo processing ispatterned by an exposure process by means of the photomask and aplurality of openings are formed in the resist that correspond to theplurality of exposure openings that are formed in the photomask, theseopenings are formed in a shape that compensates for the anisotropicdeformation that occurs when the resist is heated to cause each of theopenings to shrink. When the resist that has been thus patterned isheated and the openings are caused to shrink, these openings areanisotropically deformed as they shrink. However, since each of theopenings has been formed in advance in a shape that compensates for thisanisotropic deformation, the openings attain the proper shape aftershrinkage and deformation.

At least a portion of exposure openings among the plurality of exposureopenings may be formed in a shape that is elongated in a direction thatis approximately orthogonal to the direction toward other exposureopenings that are close. At least a portion of exposure openings amongthe plurality of exposure openings may also be enlarged in a directionthat is approximately orthogonal to the direction toward other exposureopenings that are close. The degree of enlargement of said exposureopenings becomes smaller as the distance among said other exposureopenings that are close becomes larger. When the plurality of openingsthat have been formed in this way are caused to shrink by heating theresist, the plurality of openings that neighbor each other attain theproper shape upon shrinking because the degree of shrinkage is smallerin the direction toward other openings while the degree of shrinkage isgreater in the direction orthogonal to this direction due to suchfactors as the surface tension of the resist.

At least a portion of the exposure openings among the plurality ofexposure openings are arranged in lines that are close together, andeach of the exposure openings that are arranged in these lines may beenlarged in the direction that is approximately orthogonal to thedirection of this arrangement.

The exposure openings may be formed in a rectangular shape in which thedirection of enlargement is the direction in which the long sidesextend.

Each of the exposure openings may be enlarged in substantially alldirections, and at least a portion of the exposure openings among theplurality of exposure openings may be formed such that the degree ofenlargement is smaller in the direction toward other exposure openingsthan other directions that are close.

At least a portion of the exposure openings among the plurality ofexposure openings may be formed as rectangles in which the short sidesextend in the direction toward other exposure openings that are closeand the long sides extend in a direction that is approximatelyorthogonal to this direction.

The term “enlargement of the openings in the resist” in this inventionassumes the dimensions before the openings are caused to shrink by thethermal flow process with respect to the final desired dimension of theopenings that have been caused to shrink by the thermal flow process,and thus indicates that the dimensions of exposure of the resist aremade greater.

For example, if the diameter of round openings that are caused to shrinkby the thermal flow process is “a” and the openings are caused to shrinkto “1/b” by the thermal flow process, the openings before being causedto shrink by the thermal flow process are circles having a diameter of“a×b,” but in the present invention, the exposure dimension of theresist openings is made “a×b” or greater in the direction ofenlargement.

In addition, the term “enlargement of exposure openings in thephotomask” in the present invention means that, when forming openings ofa desired dimension in the resist, the exposure openings are made largerthan dimensions that are designed based merely on these openings. Forexample, in a case in which the diameter of circular openings that arecaused to shrink by the thermal flow process as described hereinabove is“a” and the openings are caused to shrink to “1/b” by the thermal flowprocess, the openings before being caused to shrink by the thermal flowprocess are circles of diameter “a×b.” If the exposure optics are equalpower, square exposure openings measuring “a×b” on each side would beformed in the photomask, but in the present invention, the exposureopenings that are formed in the photomask are rectangles in which theshort sides are “a×b” in length and the long sides are longer than“a×b.”

Furthermore, “approximately all directions” in the present inventionmeans substantially all directions involved in the formation of theexposure openings and includes 360° of the two-dimensional directionsthat are parallel to the surface of the photomask, the four directionsto the left and right and forward and rear that are parallel to thesurface of the photomask, and the two directions that are parallel tothe four sides of the exposure openings that are formed in a rectangularshape.

The pattern forming method according to another aspect of the presentinvention is a pattern forming method used in a thermal flow process inwhich: a resist is applied to a surface of the layers of a semiconductorintegrated circuit that is to undergo processing; the resist ispatterned to form a plurality of openings in the resist; and the resistthat has been patterned is heated to cause each of the openings toshrink; wherein at least a portion of exposure openings among saidplurality of exposure openings are formed in shapes so that saidopenings are caused to become corresponding desired shapes due toanisotropic deformation that occurs in said openings when said resistthat has been patterned is heated to cause said openings to shrink.

The pattern forming method according to another aspect of the presentinvention is a pattern forming method used in a thermal flow process inwhich: a photomask is prepared in which a plurality of exposure openingsare formed; a resist is applied to a surface of the layers of asemiconductor integrated circuit that is to undergo processing; thisresist is patterned by an exposure process through the photomask to forma plurality of openings in the resist that correspond to the exposureopenings; and the patterned resist is heated to cause each of theopenings to shrink; wherein the photomask of the present invention isused during the exposure process.

According to another aspect of the present invention, a prescribedportion of a semiconductor integrated circuit having fine planar shapesis treated by a prescribed process through openings in a resist thathave been formed by the method of forming patterns of theabove-described invention.

The above and other objects, features, and advantages of the presentinvention will become apparent from the following description withreference to the accompanying drawings which illustrate examples of thepresent invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C and FIGS. 2A-2C are schematic vertical section frontal viewsshowing a semiconductor integrated circuit that is to undergo processingfor explaining an example of a thermal flow process of the prior art;

FIG. 3A is a plan view showing an example of a photomask of the priorart;

FIG. 3B is a plan view showing a resist in which openings have beenformed by exposure using the photomask shown in FIG. 3A;

FIG. 3C is a plan view showing the state of openings that have beencaused to shrink by heating the resist shown in FIG. 3B;

FIG. 4A is a plan view showing one embodiment of the photomask accordingto the present invention;

FIG. 4B is a plan view showing a resist in which openings have beenformed by exposure using the photomask shown in FIG. 4A;

FIG. 4C is a plan view showing the state of openings that have beencaused to shrink by heating the resist shown in FIG. 4B;

FIG. 5 is a characteristics chart showing the degree of deformation ofthe openings caused by heating of the resist;

FIG. 6A is a plan view showing the first modification of the photomaskaccording to the present invention;

FIG. 6B is a plan view showing the resist in which openings have beenformed by exposure using the photomask shown in FIG. 6A;

FIG. 6C is a plan view showing the state of openings that have beencaused to shrink by heating the resist shown in FIG. 6B;

FIG. 7 is a plan view showing an actual example of the dimensions ofeach part of a photomask according to the present invention;

FIG. 8A is a plan view showing a modification of the exposure patternformed on the resist;

FIG. 8B is a plan view showing the pattern of openings that are formedon the photomask of the prior art; and

FIG. 8C is a plan view showing the pattern of openings that are formedon a photomask of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment according to the present invention will be described belowwith reference to FIGS. 4A-4C and FIG. 5. Components of this embodimentthat are identical to components of the above-described example of theprior art are identified by the same term, and detailed explanation isomitted.

As shown in FIGS. 4A-4C, photomask 200 of this embodiment is also usedto pattern resist 201 in a thermal flow process, and a plurality ofexposure openings 202 are formed corresponding to the processingpositions of a semiconductor integrated circuit (not shown in thefigure) that is to undergo processing.

In more detail, in the pattern forming method of this embodiment, forexample, nine openings 203 arranged in three rows and three columns areformed in resist 201, which is applied to the surface of semiconductorintegrated circuit, as shown in FIG. 4C. The distances between theseopenings 203 is relatively small in the direction from front to back(vertical direction in the figure) and relatively large in the directionfrom left to right.

In the present embodiment as well, nine exposure openings 202 are formedon photomask 200 in three rows and three columns that are close to eachother in the front and rear directions but distant from each othertoward the right and left, as shown in FIG. 4A, but these exposureopenings 202 are formed in a shape that compensates for the anisotropicdeformation that occurs in openings 203 when resist 201 is heated tocause openings 203 to shrink.

In other words, in photomask 200 of this embodiment, each of theplurality of exposure openings 202 that are close to each other in thefront and rear directions but distant from each other toward the leftand right is formed in a rectangular shape, which is a square that hasbeen enlarged toward the right and left. As a result, in photomask 200of this embodiment, each of the plurality of exposure openings 202 thatare close to each other toward the front and rear and arranged in linesis enlarged toward the left and right, which are directions orthogonalto the direction of arrangement. As a result, these exposure openings202 are formed as rectangles having long sides that extend in the leftand right directions, which are the directions of enlargement, and thesides that extend in the front and rear directions toward the othernearby exposure openings 202 are therefore the directions in which theshort sides of these rectangles extend.

In the pattern forming method of this embodiment, however, each of theplurality of exposure openings 202 of photomask 200 is actually enlargedin almost all directions compared to the dimensions of opening 203 forthe exposure process in resist 201. However, the degree of enlargementof these exposure openings 202 is small in the front and rear directionsthat extend toward other closely neighboring exposure openings 202, andexposure openings 202 are thus formed as shapes that are expanded towardthe left and right.

Exposure openings 202, which are arranged both toward the front and rearand toward the right and left of photomask 200 as described in theforegoing explanation, are also close to each other toward the right andleft, although not as close as toward the front and rear, and exposureopenings 202 are therefore also enlarged toward the front and rear,which is the direction orthogonal to the right and left. As describedabove, however, the degree of enlargement of exposure openings 202 isgreat toward the left and right and small toward the front and rear, thedegree of enlargement in each direction being inversely proportional tothe distance to a neighboring opening in that direction.

A brief explanation is next presented regarding a thermal flow processthat uses photomask 200 of this embodiment in the above-describedconstruction.

First, resist 201 is applied to the surface of the semiconductorintegrated circuit that is to undergo processing, and this resist 201 isthen patterned by means of an exposure process by photomask 200.

Then, as shown in FIG. 4B, a plurality of openings 203 corresponding tothe plurality of exposure openings 202 of photomask 200 are formed inresist 201. When this resist 201 is heated and each of openings 203 iscaused to shrink, openings 203 of resist 201 attain a small diameterthat is less than the exposure limit dimensions, whereby a desiredprocess can be performed in a fine area of a semiconductor integratedcircuit.

When resist 201 is heated and each of openings 203 is caused to shrinkas described hereinabove, however, anisotropic deformation occursaccording to the positional relationship between these openings 203. Thedeformation of these openings 203 is believed to arise due to suchfactors as the surface tension of resist 201. When openings 203 arecaused to shrink by heating resist 201, the degree of shrinkage inopenings 203 that are close to each other is small in the directionstoward the other openings while the degree of shrinking is great in thedirection that is orthogonal to this direction, as shown in FIG. 5.

However, since exposure openings 202 in photomask 200 of this embodimentare formed in shapes that compensate for the anisotropic deformation ofopenings 203 as shown in FIG. 4A, openings 203 that are formed in resist201 by an exposure process that uses this photomask 200 are formed in anoval shape that is enlarged in the direction that is substantiallyorthogonal to the direction toward other openings 203 that are close, asshown in FIG. 4B. When the plurality of openings 203 that are thusformed are caused to shrink by heating resist 201, openings 203 assume asubstantially circular shape as shown in FIG. 4C due to the occurrenceof anisotropic deformation according to the positional relation betweenthe openings.

As a result, fine openings 203 can be formed in a proper shape in resist201 in a thermal flow process that uses photomask 200 of thisembodiment, and appropriate processing can thus be realized in a finearea of semiconductor integrated circuit. In photomask 200 of thisembodiment, moreover, each of exposure openings 202 is formed as arectangle in which the right and left directions, which are thedirections of chief enlargement, are the directions in which the longsides extend, and the design and fabrication of of the photomask is thusfacilitated.

The present invention is not limited to the above-described embodiment,and various modifications are possible in the scope or spirit of theinvention. For example, in the above-described embodiment, an examplewas described in which openings 203 of a desired shape were formed onresist 201 by a photolithographic technique using photomask 200, butthese openings 203 may also be formed on resist 201 by a direct writingtechnique that does not use photomask 200.

Although a case was described in the above-described embodiment in whichopenings 203 that were formed on resist 201 were arranged in linesextending toward the front and rear, openings 203 may also arrangedlinearly in a direction that is at an angle, as in the previouslydescribed example of ¼-pitch DRAM of the prior art. Simply adapting theabove-described photomask 200 to this type of arrangement, however,means that the exposure openings that were originally square must beenlarged in a direction that extends at an angle. The exposure openingsmust therefore be enlarged to form a parallelogram or diamond shape, andthis complicates the design and fabrication of the photomask.

When this becomes a problem, a plurality of exposure openings 211 ofphotomask 210 are formed in rectangular shapes in which the long sidesextend in an oblique direction that is orthogonal to direction ofarrangement of these openings 211.

In this case, a plurality of openings 212 are formed as inclined ovalshapes in resist 201 as shown in FIG. 6B, and these oval openings 212are enlarged in directions that are orthogonal to the direction in whichthe openings are close to each other, whereby these openings 212 becomeproper circles when caused to shrink by heating resist 201.

The inventors of the present invention actually produced photomask 210on an experimental basis in which openings 212 in resist 201 werearranged in a 45° direction as described in the foregoing explanation.In this case, the average diameter of openings 212 in resist 201 thatwere caused to shrink by heating resist 201 was set to 0.15 μm, and thepitch toward the front and rear as well as to the right and left of theplurality of openings 212 that were arranged in a 45° direction was setto 0.3 μm.

Taking into consideration the data of FIG. 5, exposure openings 211 ofphotomask 210 were formed in rectangular shapes with short sides of 0.23μm and long sides of 0.4 μm as shown in FIG. 7, and it was confirmedthat openings 212 were finally formed having substantially theabove-described dimensions.

In the above-described embodiment, an example was described in whichregularly arranged openings 203 were formed in resist 201, but thepresent invention may also be adapted to a case in which irregularlyarranged openings 203 are formed in resist 201. It is also obvious thatthe conditions of deformation for openings of identical shape that arearranged in a line at uniform intervals as described hereinabove willdiffer for openings at the two ends and for openings in the centralarea.

However, the inventors designed photomask 222 in which all of openings221 can be formed in proper shape assuming three openings 221 having adiameter of 0.2 μm are arranged in resist 201 in a line at a pitch of0.35 μm as shown in FIG. 8A.

In a photomask of the prior art in such a case, three square exposureopenings measuring 0.2 μm on each side are arranged in a line at a pitchof 0.35 μm as shown in FIG. 8B. In contrast, it was confirmed that inphotomask 222 of this invention, central exposure openings 223 arepreferably formed as rectangles measuring 0.24×0.30 μm and exposureopenings 223 at the two ends are preferably formed as rectanglesmeasuring 0.27×0.30 μm, as shown in FIG. 8C. In other words, in a casein which a plurality of exposure openings 223 are arranged in a line,the degree of enlargement in the direction of arrangement of exposureopenings 223 at both ends is preferably greater than the degree ofenlargement of exposure openings 223 in the central area.

Among the above-described embodiments, a case was described in whichexposure openings 202 of photomask 200 were enlarged in substantiallyall directions, i.e., toward the front, rear, left and right, with thedegree of this enlargement for the front-rear directions differing fromthat for the left-right directions. However, it is also possible forexposure openings 202 to be enlarged in only specific directions.

While preferred embodiments of the present invention have been describedusing specific terms, such description is for illustrative purposesonly, and it is to be understood that changes and variations may be madewithout departing from the spirit or scope of the following claims.

What is claimed is:
 1. A method of forming patterns for use in a thermalflow process in which: a resist is applied to the surface of a layer ofa semiconductor integrated circuit that is to undergo processing; saidresist is patterned to form a plurality of openings in said resist; andsaid resist that has been patterned is heated to cause each of saidopenings to shrink; wherein at least a portion of exposure openingsamong said plurality of exposure openings are formed in shapes so thatsaid openings are caused to become corresponding desired shapes due toanisotropic deformation that occurs in said openings when said resistthat has been patterned is heated to cause said openings to shrink.
 2. Amethod of forming patterns according claim 1 wherein at least a portionof openings of said plurality of openings are formed in shapes that areelongated in a direction that is approximately orthogonal to thedirection toward other said openings that are close.
 3. A method offorming patterns according to claim 2 wherein at least a portion ofopenings among said plurality of openings are enlarged in a directionthat is approximately orthogonal to the direction toward other saidopenings that are close.
 4. A method of forming patterns according toclaim 2 wherein, when at least a portion of openings among saidplurality of openings are arranged in lines that are close together,each of said openings that are arranged in these lines is enlarged in adirection that is approximately orthogonal to the direction of saidarrangement.
 5. A method of forming patterns according to claim 2wherein at least a portion of openings among said plurality of openingsare enlarged in substantially all directions such that the degree ofenlargement is smaller in the direction toward other openings that areclose than other directions.
 6. A method of forming patterns accordingto claim 5 wherein at least a portion of openings among said pluralityof openings are formed as rectangles in which the short sides extend inthe direction toward said other openings that are close and the longsides extend in a direction that is approximately orthogonal to thisdirection.
 7. A method of forming patterns according to claim 3 whereinthe degree of enlargement of said openings is in inverse proportion tothe distance to said other exposure openings that are close.
 8. A methodof forming patterns according to claim 3 wherein said openings areformed in rectangular shapes in which the direction of enlargement isthe direction in which the long sides extend.
 9. A method of formingpatterns for use in a thermal flow process in which: a photomask isprepared in which a plurality of exposure openings are formed; a resistis applied to the surface of a layer of a semiconductor integratedcircuit that is to undergo processing; said resist is patterned by anexposure process through said photomask to form a plurality of openingsin said resist that correspond to each of said exposure openings; andsaid resist that has been patterned is heated to cause each of saidopening to shrink; wherein at least a portion of exposure opening amongsaid plurality of exposure openings are formed in shapes so that saidopenings are caused to become corresponding desired shapes due toanisotropic deformation that occurs when each of said openings is causedto shrink by heating said resist on which the patterning has beencarried out.